Field of the Invention
The invention relates to a circuit configuration for converting TTL-level signals into CML or ECL-level signals.
In numerous applications, there is a need to supply signals from circuits in transistor-transistor logic (TTL) to circuits in current-mode logic (CML) or to circuits in emittercoupled logic (ECL). However, such a signal supply is not readily performed because the signal levels of the various circuit types are different. The greatest differences arise between the TTL level and the CML or ECL level, while the CML and ECL levels are more like one another. This can be easily explained in terms of the voltage ranges necessary for the particular logic state. The voltage equivalent to the L state is between -1.2 V and +0.8 V in TTL, it is approximately -0.5 V in CML, and it is approximately -1.3 V in ECL. The voltage equivalent to the H state is between +2.0 V and +5.5 V in TTL, it is approximately equal to 0 V in CML, and it is approximately -0.8 V in ECL. Special circuit configurations are therefore required in order to adapt the very different levels to one another.